SWCNT growth on Al/Fe/Mo investigated byin situmass spectroscopy

Abstract

The effect of temperature on the growth of single-walled carbon nanotubes (SWCNTs) was investigated over the range of 725–900 °C. A cold-wall reactor consisting of a heated stage (on which the substrate for SWCNT growth (Al/Fe/Mo) was placed) and a showerhead (from which C2H2 was introduced vertically into the reactor) was used for the growth. The heating was found to play two roles: (1) it generated complex hydrocarbon radicals during the growth process, as well as (2) promoting catalytic nanoparticles on the substrate during the annealing process. The optimum temperature for the highest SWCNT yield was found to be ∼860 °C. For the first time, in situ mass spectroscopy was used to identify the growth precursors generated from thermal pyrolysis of C2H2 within this temperature range. The peak of the radicals found (C6H9, C5H9 and C6H13) and the highest catalyst support particle density (Fe catalyst supported on AlxOy) was correlated to the maximum yield of single walled carbon nanotubes at the optimum growth temperature of ∼860 °C. Bottom gate SWCNT-FETs (single-walled carbon nanotube based field effect transistors) were fabricated showing a high transconductance of ∼0.12 µS and on/off ratio of ∼105 which are both comparable to other state-of-the-art SWCNT-FET.

Optical in situ characterisation of carbon nanotube growth

“…A few methods capable of studying the growth in situ have been reported. Among them are optical registration of film thickness and surface pyrometry (Puretzky A A 2008, Jönsson et al, 2007), Raman spectroscopy (Kaminska et al, 2007, Li-Pook-Than et al, Dittmer et al, 2008c, Picher et al, 2009, mass spectrometry of by-product gases (Kim, 2007, Meshot et al, 2009 and electron microscopy (Yoshida et al, 2008, Sharma andIqbal, 2004). Electron microscopy can provide detailed structural information although the growth conditions are usually not comparable to the conditions typically used for growing CNT.…”

Early Evaluation of Potential Environmental Impacts of Carbon Nanotube Synthesis by Chemical Vapor Deposition

“…To date, publicly available effluent analyses have relied on relatively insensitive techniques, such as residual gas analysis (ppmv detection limits) − . For example, online analysis of an ethyne-fed CNT production revealed a handful of incompletely identified byproducts: cyclohexane, a “cyclopentane fragment”, and a “hexane fragment” .…”

“…To date, publicly available effluent analyses have relied on relatively insensitive techniques, such as residual gas analysis (ppmv detection limits) − . For example, online analysis of an ethyne-fed CNT production revealed a handful of incompletely identified byproducts: cyclohexane, a “cyclopentane fragment”, and a “hexane fragment” . An offline analysis of a different ethyne-based CNT synthesis tentatively identified methane and several unsaturated hydrocarbons (specifically, ethene, 1-buten-3-yne, pent-3-en-1-yne, two hexadiene-yne isomers, benzene, toluene, and cyclooctatetraene) .…”

Investigation of modified nanopore arrays using FIB/SEM tomography

“…To visualize the pore shape and inner pore space of SiN membrane-supported nanopores, high-resolution transmission electron microscopy (TEM) tomography has been employed. 41,42 In contrast to TEM, FIB/SEM tomography 43 enables the reconstruction of large sample sections with a resolution down to several nanometers. 44,45 FIB-milled cross-sections of nanopores have been published by Liu et al in order to investigate the shape of the nanopores, especially with respect to electron-or ion beam-induced shrinking.…”